Drop foot is a gait abnormality in which the forefoot drops due to weakness, irritation, or damage to the common fibular nerve including the sciatic nerve, or paralysis of the muscles in the anterior portion of the lower leg. Drop foot may be characterized by an inability or impairment to raise the toes or a foot relative to an ankle in dorsiflexion, or inversion or eversion of the foot. The foot hangs with toes pointing down, causing the toes to scrape the ground while walking, and requiring the individual to lift the corresponding leg higher than normal when walking to avoid slapping the foot on the ground. Drop foot is highly pronounced in the part of the gait cycle that involves the most dorsiflexion, such as at heel contact and during the swing phase.
Drop foot may be temporary or permanent depending on muscle weakness or nerve damage or impairment, and most commonly affects one side only although it can affect both sides, either equally or to different degrees.
Drop foot can be caused by nerve damage alone or by muscle or spinal cord trauma, neurological dysfunction, abnormal anatomy, complications relating to surgery (i.e., hip or knee), or disease. Diseases that can cause drop foot include direct hit to posterolateral neck of fibula stroke, amyotrophic lateral sclerosis (ALS or Lou Gehrig's Disease), muscular dystrophy, Charcot Marie Tooth disease, multiple sclerosis, cerebral palsy, hereditary spastic paraplegia and Friedreich's ataxia.
Ankle-foot orthoses may treat drop foot by controlling the position and motion of the ankle. An ankle-foot orthosis may be constructed from plastic and possess the shape of an “L” with the upright portion behind the calf and the lower portion running underneath the foot. Alternatives may include jointed ankles and may provide different control. These alternative ankle-foot orthoses are often custom formed and are bulky, particularly when worn with clothing and shoes.
In a prior art orthopedic device in FIGS. 1A and 1B, drop foot orthosis 2 is provided with a first attachment member or ankle component 4 for attachment of the drop foot orthosis 2 to the lower leg, a second attachment member or foot component 6 for attachment of the drop foot orthosis 2 to an upper side or instep of a shoe 8 enclosing the foot-drop affected foot, and a strap assembly joining the first and second attachment members 4, 6. The second attachment member 6 is provided with an attachment plate or inlay 7 which, in use, is positioned under the upper part or instep (such as a tongue, shoe lace or edge) of the shoe 8 (see FIG. 1B). The user, when walking, experiences an upward (supporting) force 36 which acts on a point near the tongue 34 of the shoe 8.
This assembly requires careful placement of the plate 7, and is generally limited to shoes having laces. The plate 7 may slide about within the shoe 8 as a user walks, and may not offer a stable connection if the shoe laces are not sufficiently tensioned. It may prove cumbersome for attaching and detaching the plate 7, particularly if the plate 7 slides about. It also precludes easy and/or one-handed adjustment. This assembly further fails to offer a user the option to adjust the orthopedic device to provide more or less medial or lateral support, as their specific condition may require. The assembly also makes it difficult to replace the strap, adjust the length of the strap to match an individual's dimensions, or to switch out the strap and plate for a different preferable strap and/or foot component or attachment.
Another problem with this assembly is that it does not allow for voluntary plantar flexion or other articulation by a user during the swing phase or provide dorsiflexion support. This reduces comfort and desirability for long-term use.
Existing strap attachment and adjustment mechanisms are frequently inadequate for holding a strap in position due to undesired slippage of the strap. This is at least in part due to most adjustment mechanisms providing a lever with a flat profile. In these devices, a component of the strap force creates a clearance between the strap attachment mechanism and lever face. Manufacturing variability also affects the ability to properly hold a strap in place without undesired slippage.
From the foregoing, there is a need for an orthopedic device that provides improved attachment between ankle and foot components, while offering better medial and/or lateral support and flexibility and ease of use.